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Can someone tell me what capacitor this is please.....?

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Boncuk

New Member
Hi bicepius,

actually there is printed ".330" on the component.

So I guess colin55 is right with his assumption: "3 - 3 and 0 zeros".

0.331 would then mean 330µH.

Boncuk
 

colin55

Well-Known Member
There is never a decimal point in any of the coding systems.
The whole idea of the number code is to eliminate the decimal point.
That's why I label all components without a decimal point.
 

Boncuk

New Member
There is never a decimal point in any of the coding systems.
Oops, WIMA must be much wrong there!

They do manufacture capacitors and they do use a decimal point.

(The anglo-saxon decimal point is replaced by a comma in the German language.)

Please correct them!


BTW, what do you imagine the big round blown up dot in front of the number of the part should represent?

Printed to get rid of excessive paint?
 

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That would be my assumption, the one thing I hate more than anything else is excessive paint. But you know what they say, assuming makes an ass out of u and me.
 

Mr RB

Well-Known Member
I believe the white dot is a pin identifier. These dots are definitely used on some TV inductors that are polarised (they have a small magnet inside).

I don't think this inductor is polarised, but the pin identifier might just be a manufacturing standard or it might be useful as some inductors have different pin radius because each of the 2 leads originates at a different radius from the package centre. So it is needed for correct insertion during manufacturing.
 

Diver300

Well-Known Member
Most Helpful Member
The axis of the coil is vertical, and one pin is at the clockwise end and the other at he anticlockwise end. The dot marks one of those. (I don't know which one)

The pin dot is needed because some of the magnetic field will come out of the coil. This will interact with other components, specifically other inductors, but the PCB and any box may have an effect as well.

That inductor is encapsulated, but on open inductors it's quite easy to add extra turns for auxiliary outputs. Fig 13 of http://www.national.com/ds/LM/LM25576.pdf shows an application and it's important to wind the extra turns the right way round, and for that the dot is really useful.

It's a bit like the polarisation of transformers or speakers, in that you only need to worry about them when other transformers or speakers are connected.
 

Mr RB

Well-Known Member
The pin dot is needed because some of the magnetic field will come out of the coil. This will interact with other components, specifically other inductors, but the PCB and any box may have an effect as well.
A minor nitpick; the magnetic field comes out the top and bottom of the coil, the pin identifier is totally irrelevant under those conditions. However I think we agree the dot is there to ensure correct insertion.
 

Diver300

Well-Known Member
Most Helpful Member
A minor nitpick; the magnetic field comes out the top and bottom of the coil, the pin identifier is totally irrelevant under those conditions. However I think we agree the dot is there to ensure correct insertion.
It's not irrelevant. If you put the current in at the pin marked with a dot, the top is a north or south pole. Put the current in the other pin and the top is the opposite pole. I don't know which way round the inductors are made, but they will all be the same.
 

RCinFLA

Well-Known Member
The dot signifies where the outside layer of the winding is.

For a simple boost or buck switcher the functionality is irrelavent to direction. There is some preference to have the outside winding surface be the terminal that goes to the output filter, or B+ bypass cap in case of boost switcher, which reduces the exposure to switching transistor transients that may radiate slightly more E-field EMI.

Non-polarized caps have a similar 'bar' marking signifying the outside foil layer terminal. The outside foil layer is preferred to be on the ground or low impedance side of circuit to reduce EMI.
 
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